Poly(vinyl butyral) (PVB) is widely used as an interlayer in laminated safety glass in automotive and construction applications. The increasing quantities of PVB arising from end-of-life laminated glass represent a waste stream with significant potential for recycling. This study investigates the durability of high-quality retrieved PVB (re-PVB) separated from laminated glass wastes and evaluates the effect of restabilization against UV aging. Neat unplasticized PVB (u-PVB) and re-PVB were subjected to artificial UV weathering (ISO 4892-3) for up to 1500 h and then characterized in terms of chemical structure, yellowness, melt flow behavior and molecular weight. The results showed that u-PVB exhibited pronounced photooxidative degradation, while re-PVB remained comparatively stable. UV–Vis spectroscopy revealed the presence of residual UV absorbers in re-PVB, indicating that the components of the initial stabilization system might remain functional after the end of its life. Unexpectedly, the restabilization of re-PVB with phenolic antioxidants (AOs) reduced its photooxidative stability, despite their established effectiveness against thermo-mechanical degradation in melt reprocessing. A possible antagonistic effect was suggested between the newly introduced AOs and the residual stabilization system. These findings highlight that re-PVB is a valuable waste, and restabilization should be carefully considered when designing its second service life.